In cutting machining, it is crucial to aim for a dynamically stable cutting process in order to provide an optimum cutting speed, surface finish, machine service life, etc. An important factor to take into consideration is the presence of vibrations or chatter, which may result in dissonance, poor surfaces of machined details, decreased service life of cutting edges, as well as may cause an unpredictable machining process. Vibrations may arise and be found in the entire cutting system that includes machine, workpiece, attachment for workpiece, tool-clamping details, as well as a tool including cutting edges. In use of long tools, or tools provided with one or more extension details or shafts, vibrations in the cutting end are extra pronounced. The presence of vibrations usually leads to a reduction of tool data, such as cutting depth, radial engagement, feed speed or cutting speed. A possible method to counteract vibrations is to reduce the number of active cutting edges in the milling tool, which then also reduces the efficiency of the tool, since it then takes a longer time to carry out the work. So-called differentially pitched milling cutters, where the milling inserts are placed at a varying pitch around the circumference of the milling cutter, are also used to reduce or prevent vibrations in the system.
Other prior art for the reduction of vibrations in tools for rotary machining, and in particular for the reduction of vibrations in milling tools, includes the introduction of a centrally placed damper in the tool body. Usually, this damper is formed from a viscoelastic material, which counteracts operation-induced vibrations in the tool. A problem of this prior art is that the damping becomes limited to a specific frequency or range of frequencies and that the damp body is tuned against a specific natural frequency of the tool system. Furthermore, the size and extension of the damp body is limited, because of the central location, in consideration of the stability and strength of the tool. This is because the centrally placed damper involves that a relatively great part of the load-carrying mass of the tool is removed. Therefore, a damped tool that solves the above mentioned problems is in great demand.
An object of the invention to provide a damped rotary tool for cutting machining. Another object of the invention is to provide a milling tool having improved damping.